Dark matter is a hypothetical type of matter that is believed to make up about 85% of the total matter in the universe. It is called "dark" because it does not interact with light or any other form of electromagnetic radiation, making it invisible to telescopes.
Dark matter was first hypothesized in the 1930s by Swiss astronomer Fritz Zwicky, who observed that the visible mass of galaxies was not enough to account for their observed gravitational effects. In the 1970s, American astronomer Vera Rubin provided further evidence for the existence of dark matter through her observations of galaxy rotation curves. More recent evidence has been gathered through observations of the cosmic microwave background radiation and the large-scale structure of the universe.
The discovery of dark matter is significant because it helps us better understand the structure and evolution of the universe. It also provides a solution to the problem of galaxy rotation curves and the overall stability of the universe. Understanding dark matter can also lead to a better understanding of other fundamental aspects of physics, such as the nature of gravity.
Dark matter is studied through various techniques, including gravitational lensing, where the gravitational pull of dark matter bends the path of light from distant objects; galaxy rotation curves, where the movement of stars in galaxies can reveal the presence of dark matter; and colliding galaxy clusters, where the separation of normal matter and dark matter can be observed. Scientists also use computer simulations to study the behavior of dark matter in the universe.
There are several theories about the nature of dark matter, but the most widely accepted one is the Cold Dark Matter (CDM) theory, which proposes that dark matter consists of slow-moving particles that were created in the early universe. Other theories suggest that dark matter may be made up of primordial black holes, axions, or other exotic particles. However, the exact nature of dark matter is still a mystery and is an active area of research in astrophysics and particle physics.